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Hydrogeologic Controls on the Occurrence of Radionuclides in Groundwater of Southern Ontario
Published in Barbara Graves, Radon, Radium, and Other Radioactivity in Ground Water, 2020
In the Bancroft and Kennebec-Sharbot Lake areas uranium minerals consist mostly of uraninite, uranophane, and allanite. They occur as accessories with pegmatites, calc-silicates, and hydrothermal vein deposits, associated with regional metamorphism of the Grenville Orogeny dated at 960-975 m.y. [2] In portions of Southeastern Ontario where the Precambrian basement is overlain by Paleozoic sedimentary rock, local concentrations of uranium have been reported in Cambro-Ordovician sandstones and dolostones. [7] Secondary uranium is found associated with bituminous sequences near the Precambrian-Phanerozoic unconformity. The model for this mineralization derives uranium from the Precambrian basement by oxidation by shallow circulating groundwater. Dissolved uranium is transported by groundwater through bedrock fractures and along the unconformity and is fixed by reduction in bituminous-rich units. [8, 9]
Phreatic uranium mineralisation hosted by Neogene sediments from the Taunsa area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan: unique exploration targets in a deformed geological setting
Published in Australian Journal of Earth Sciences, 2021
R. Ullah, F-J Nie, C-Y Zhang, X. Zhang, Z-B Feng
Uranium-bearing phases associated with Fe–Ti-oxides indicate up to ∼29 wt% TiO2 and 29 wt% UO2, which correspond closely to brannerite compositions (Frondel, 1958), i.e. TiO2: 32 to 39 wt% and UO2: 32 to 52 wt%. Brannerite can form in sedimentary environments following initial adsorption of uranium onto TiO2 phases (Finch & Murakami, 1999). Brannerite is also reported as a dominant uranium mineral, followed by coffinite and uranium oxides in abundance, in the sandstone-type deposit in the ISR site at Rosita, Texas, USA in a complex relationship between U–Ti minerals and sulfide/silicate phases with the uranium phases as inclusions and irregularly developed veins or intergrowths (Brown et al., 2015). The direct reduction of U(VI) by Fe–Ti oxides to form brannerite and other uranium phases in the Rosita uranium ore (Brown et al., 2015) is novel and unlike earlier and prevailing models of the formation of sulfide phases from alteration of Fe–Ti oxides, which in turn act as the main U(VI) reductants. Brannerite is also reported with uraninite and uranophane in the MingQiGuEr roll-front uranium deposit, Yili Basin, China (Shabaga et al., 2011). However, brannerite is suggested to form at high temperatures, unlike the low-temperature sedimentary environments at the Taunsa uranium ore (M. Cuney, personal communication, September 14, 2020).